The term stripline as used herein, generally refers to structures which include a layer of dielectric material having opposing surfaces on which respective layers of electrically conductive material are disposed. One or more resonators are sandwiched within the dielectric layer to fabricate a stripline filter structure.
Generally, stripline filters can have various frequency responses which can resemble bell-shaped curves and the like.
Stripline filters are typically used as injection filters, for example, and include a frequency response characteristic with a desired bandpass. Each conductive strip defines a pole in the transfer function of the filter.
A conventional wide bandwidth filter can be modified, as described more fully herein, by making certain adjustments in the design. A wider bandwidth reduces the insertion loss of the filter, but, it also reduces the filter's attentuation of the unwanted frequency. The addition of a transmission zero in the transfer function at the frequency of the unwanted signal, could effectively improve the performance of a stripline filter, as described herein.
It is considered an improvement in the art, if a structure could be devised which could modify stripline filters, to create an inductive transmission line near the grounded end of the resonators, to provide a high side zero transfer function.
The addition of a transmission zero in the transfer function at the frequency of the unwanted signal, could improve the performance of a stripline filter.